Electro-optic systems comprised of optical fibers and electro-optic components are used in a wide variety of commercial applications, such as data-communications.
The optical fibers which are commonly employed have a relatively small diameter core comprised of an optically transparent material, e.g. glass or plastic, surrounded by a protective cladding layer of glass or a polymeric material. A glass optical fiber having a glass cladding layer may have an additional thin layer of a polymeric material to prevent microcracking. Since optical fibers are relatively weak, they are subject to breakage when strain is applied to them. Even if strain applied to an optical fiber within an electro-optic system does not break the optical fiber, it can force the terminal end thereof out of alignment with an electro-optic component, causing the system to become inutile. Optical fibers are conventionally protected by being encased in a fiber optic cable. The most commonly employed type of fiber optic cable has an optical fiber in the center, a plurality of reinforcement strands positioned circumferentially about the optical fiber and aligned with the length of the optical fiber so as to be capable of relieving strain on the optical fiber, and an outer jacket disposed over and about the reinforcement strands.
The electro-optic components of an electro-optic system include many different types of devices, such as light emitters, light detectors, signal repeaters and the like. Many of the electro-optic components are highly sensitive to environmental contaminants and are highly susceptible to physical damage. To prevent damage, the components are sealed in protective component housings which are made in various configurations to accommodate the different types of devices. All component housings include an opening for passage of an optical fiber to the interior.
When connecting a fiber optic cable into an electro-optic system, a terminal end of the optical fiber must be precisely aligned with the electro-optic component packaged in a component housing and secured in position. The component housing is then hermetically sealed and the remaining portions of the fiber optic cable, that is, the reinforcement strands and the jacket, are trimmed and secured to the component housing by mechanically crimping or by a length of heat-shrink tubing.
The securing of fiber optic cables to the component housings presents serious production and performance problems. In order for the fiber optic cable to protect the optical fiber from strain, the ends of the reinforcement strands must be locked in position so as to absorb any strain placed on the fiber optic cable. Certain of the suggestions heretofore made for fiber optic terminations required a relatively complex series of steps by a skilled operator to make an even marginally satisfactory termination. Other suggestions involved introducing another optical interface with special fittings similar to those used to couple lengths of fiber optic cable together, which couplings produced an excessively large connection. The most serious problem encountered with the suggested methods was that they did not provide adequate strain reief so as to prevent breakage and misalignment of the optical fibers with the components.
In a previous patent application, Ser. No. 785,790, filed Oct. 9, 1985, (now U.S. Pat. No. 4,640,725). I have disclosed a method of making a termination of a fiber optic cable of the above-described type with a component housing wherein a predetermined length of the outer jacket is removed from the cable, the optical fiber is inserted into and through a tubular extension of a component housing and retained in place. The reinforcement strands of the cable are then separated into at least two groups, and positioned to partially cover the tubular extension. A layer of adhesive and a cover of, e.g. heat-shrink tubing, are then applied to cover the tubular extension and fiber cable. In accordance with this invention, an improvement is provided in the method of my prior application which facilitates reliable assembly and substantially strengthens the termination.